Apparatus for cooling electron discharge devices



March 30, 1954 F. R. DICKINSON 2 APPARATUS FOR COOLING ELECTRONDISCHARGE DEVICES Filed April. 13, 1951 m/ l EN TOR E R. DICKINSONATTORNEY Patented Mar. 30, 1954 APPARATUS FOR COOLING ELECTRON DISCHARGEDEVICES Frank R. Dickinson, Glen Ridge, N. J assignor to Bell TelephoneLaboratories, Incorporated, New York, N. Y., a corporation of New YorkApplication April 13, 1951, Serial No. 220,952

1 Claim. 1

tion requires accessory equipment including a l blower. When tubes areplaced in unattended substations it is undesirable to employ anymachinery that would require maintenance, as would the rotatingmachinery and other parts of the blower equipment. Additionally, it isoften desirable to connect the unit in which the tubes are incorporated,such asan amplifiendirectly and solely into the circuit. Thus in coaxialcables the amplifier may be contained in a sealed case connecteddirectly into the coaxial cable Without any outside power supply. Thenall the power to the amplifier must be transmitted over the cableitself. But the power requirements of a blower would be such that thepower for the blower could not be transmitted over the cable and outsideelectrical connections would be necessary.

Without a forced air cooling the ventilation of tubes, and particularlywhen in a closed case, may not be sufficient to cool the tube envelopes.Heat may also be dissipated by radiation from the tube envelope or byconduction. The heat loss through radiation is not significant norgenerally is that through conduction as the tube envelope is not incontact with any other bodies. Thus without forced air cooling the heatdissipation from a thermionic tube by conduction, convection, andradiation is insufiicient for many purposes.

It is important to reduce the temperature of tubes in order to preventdecrease of their operating lifetimes. Particularly when such tubes areplaced in closed units for unattended operation it is desirable to havea long tube life in order to reduce the maintenance necessary to anabsolute minimum. Thus a maximum amount of heat dissipation from thetube is desirable.

It is one object of this invention to increase the life of thermionictubes, and particularly such tubes in unattended units.

It is a further object of this invention to increase the heatdissipation from vacuum. tubes without forced air cooling.

It is a still further object of this invention to substantially lowerthe temperature of the envelope of a thermionic vacuum tube by increasing the conduction of heat therefrom.

These and other objects of this invention are achieved by positioning ashield of a good heat conducting material around the vacuum tube. Aplurality of helically wound springs are arranged within the shield andmake contact with the glass envelope of the tube in the region of oropposite the internal elements of the tube. These springs thus haveturns extending between the glass envelope of the tube and the innersurface of the shield. Each turn of the helical spring makes aconduction contact with the envelope of the tube, and each such contactis provided with two parallel heat conduction paths to the shield. ByWinding the springs fairly tightly a considerable number of suchconduction points and paths are provided to conduct heat from theenvelope of the tube to the shield. The shield in turn is mounted on agood heat conduction base or mounting chassis to Which the heat isdissipated.

The envelopes of tubes can generally be considered to be cylindrical butactually in the mass production of tubes eccentricities are oftenintroduced so that the envelopes instead of being circular in crosssection are more nearly oval or el liptical. Additionally, thetemperature attained by the thermionic tube during operation may affectthe glass envelope so that it does not retain its form but changes,accentuating the eccentric configuration. Also, in actual massproduction the tubes are not all accurately centered on the pins in thebase of the tube so that, on being placed in their sockets, the actualpositions of the envelopes will vary. However, the springs which providethe conduction paths between the glass envelope and the shield, which ofcourse is and remains always cylindrical, are flexible enough to allowfor considerable variations without there beingany loss of contactpoints with bulb or envelope of the tube.

ihe shield itself serves a dual function as it not only quickly removesthe heat of the tube to itself by conduction along the helical springs,in accordance with this invention, but also it acts as an electrostaticand electromagnetic shield, as is Well known and as is generallynecessary for many tube applications.

It is therefore afeature of this invention that conduction paths beprovided between the glass envelope of a vacuum tube and an outer shieldby a helical spring extending around the envelope and making contacttherewith at a number of points.

It is a further feature of this invention that the envelope of thevacuum tube depress the inner turns of the helical spring so thatconsiderable variations in the diameter and concentricity of the tubeenvelope can be accepted without loss of any points of thermal contactwith the helical spring.

It is a further feature of this invention that the heat conductingshield surrounding the vacuum tube be mounted on a heat dissipating baseand comprise a plurality of helical springs within the shield contactingthe inner surface of the shield and contacting the envelope of thevacuum tube at a large number of distinct points. In accordance withthis feature, the springs define two parallel heat conduction paths fromeach of these points to the shield and thus to the heat dissipatingbase.

A complete understanding of the invention and the various desirablefeatures thereof may be gained from consideration of the followingdetailed description and accompanying drawing, in which: Fig. 1 is aperspective view of one heat conducting shield illustrative of thisinvention mounted on a heat dissipating base and with a vacuum tubepositioned therein; and

Fig. 2 is a side view of the assembly of Fig. 1, a portion of the shieldbeing broken away to show the helical spring members contacting theenvelope of the vacuum tube and the inner surface of the shield.

Referring now to the drawing, the shield 19 may advantageously be ahollow cylinder of slightly larger inner diameter than the outerdiameter of the glass envelope of the tube with which it will beemployed. It may advantageously be of copper or other good heatconducting material and is supported in good thermal contact with a baseII, also advantageously of good heat conducting material, as by an innerring member I2 having fingers I3 extending upward and clamping ears l4integral with the shield 10 and extending inward therefrom at its base.

A vacuum tube or other electronic device 16 is mounted in a socket I!supported by the base ll. Metallic conduction of heat away from theenvelope of the tube 6 to the shield l and thence to the base II isaccomplished by helical springs 20 which are held in shallow grooves 2|around the inner periphery of the shield by wire or snap springs 22. Theaxes of the helices are thus circles concentric with the cylindricalshield ID. The helical springs and snap springs 22 may advantageously beof steel.

When the vacuum tube I6 is positioned within the shield I0 by beingmounted in its socket 11, the envelope of the tube bears against theinner portions of the turns of the helical springs 20 biasing them andthus slightly depresses them. Each turn of each helical spring thusmakes contact with the glass envelope of the tube at one contact pointand from that contact point two heat conducting paths are provided backto the shield In. A good thermal connection is made between the shieldI0 and the turns of the'springs 20 by the relatively long portions ofthe spring coils held tightly in the grooves 2| by the snap or wiresprings 22.

Variations in the initial configuration of the tube envelope, such aslack of concentricity or differences in external diameter, are taken upby the flexible springs 20 which adjust to each particular tube. Thedifferences in tube dimensions will only result in different amounts ofdepressions of the inner portions of the turns of the helical springs.Similarly, any change in the external configuration of the tube duringoperation because of the internal generation of heat will be compensatedfor as the springs follow the variat ons in the envelope without losingany points of contact therewith.

In one specific embodiment of this invention intended for use in acoaxial cable amplifier incorporated in a sealed case and located inisolated and unattended huts, the shield 10 was of .065 inch coppertubing, 1% inches high and 1 /2 inches in diameter, the springs 20 wereof .010 inch steel wire helically wound with 20 turns per inch and thesnap springs 2| were of .055 inch steel wire. The base II was of copperand attached to the amplifier case so that the amplifier case alsodissipated the heat conducted to it from the tube envelopes through thegood metallic conduction paths of the springs 2!), the shield I0 and thebase i I.

With this specific illustrative embodiment of this invention whenemployed with amplifier tubes, such as triodes or pentodes, reductionsin the temperature of the tube envelope of over 70 C. are easilyattained. I

It is to be understood that the above-described arrangements areillustrative of the principles of the invention. Cther arrangements maybe devised by those skilled in the art without departing from the spiritand scope of the invention.

What is claimed is: g

Means for conducting heat from the envelope of an electron dischargedevice to a base member of heat conducting material which dissipates theheat conducted to it from the envelope, comprising a cylindrical shieldof heat conducting material attached to and in. thermal contact withsaid base member and surrounding the device, the inner periphery of saidshield having a plurality of circular grooves therein, a plurality ofhelical springs Within said grooves, the axes of the helices of saidsprings being circles concentric with said shield, and spring meanspositioning said helical springs in said grooves in thermal contact withsaid shield, the turns of said springs away from said shield beingdepressed by the envelope of the electron discharge device, makingcontact with said envelope at a plurality of points and defining twoparallel heat conductive paths from each of said points to said shield.

FRANK R. DICKINSON.

References Cited in the file of this patent UNITED STATES PATENTS NumberName 7 Date 750,885 Nelson Feb. 2; 904 1,191,191 Kitchen July 18. 19161,716,743 Still June 11, 1929 2,443,179 Grandmont et a1. Dec. 24, 19462,513,828 Usselman et a1 July 4, 1950 FOREIGN PATENTS 7 Number CountryDate 113,331 Great Britain Aug. 21, 1917

